1. Field of the Invention
The present invention relates generally to membrane clamping arrangements for use in loudspeakers, and more particularly, to a loudspeaker membrane clamping structure that allows the usage of a totality of the volume of available air contained within the loudspeaker to reduce the dimensions of the loudspeaker.
2. Description of Related Art
Known loudspeaker compression drivers comprise a membrane that is clamped between a magnet structure and a cover. A mechanical annular clamp is used to hold the membrane in place on the magnet structure without interfering with movement of a convex body portion of the membrane. One economical prior art method of holding the membrane in place on the magnet structure comprises providing an annular ring configured to extend around the membrane. The ring has a continuous upwardly projecting rib that extends along its upper surface. An interior surface of the cover is configured with a downwardly projecting rib that is aligned with the upwardly projecting rib of the ring, when the cover is coupled to the magnet structure. With the cover coupled to the magnet structure, the cover's rib exerts a clamping force on the rib of the ring which presses the ring tightly against the membrane and magnet structure, for securing the membrane against the magnet structure and prevent relative movement therebetween.
However, a disadvantage of this method is that the two ribs are in continuous contact along their abutting surfaces and form an isolated central cavity and a peripheral cavity. The central cavity being defined by the inner periphery of each of the ribs, a portion of the cover's interior surface located within the inner periphery of the cover's rib, and the body of the membrane. The peripheral cavity is defined by the exterior periphery of the ribs, a portion of the cover's interior surface extending between the exterior periphery of the ribs and an outer edge thereof, and a surface of the magnet structure extending between the exterior periphery of the ribs and an outer edge thereof having the cover's outer edge coupled thereto. Since a first volume of air, located within the central cavity, is isolated from a second volume of air, located in the peripheral cavity, the quantity of available air into which the membrane radiates is substantially limited.
An alternative method for securing the membrane to the magnet structure comprises disposing a plurality of fasteners, such as screws, through a back of the magnet structure. The membrane is then positioned on the magnet structure and the fasteners are actuated to engage the membrane, for securing the membrane to the magnet structure. However, a disadvantage of utilizing fasteners for securing the membrane to the magnet structure is that it is somewhat cost intensive.
Further, prior art attempts have been made to reduce the size of the cover. Reducing the size of the cover, which typically comprises die-cast aluminum, would be advantageous for a number of reasons. Most notably, the amount of aluminum that is required to fabricate the cover could be reduced and the overall dimensions of the loudspeaker can also be reduced, resulting in a space savings. Unfortunately, when the size of the cover is reduced, the size of the central cavity, formed when the cover is secured to the magnet structure, into which the membrane radiates is similarly reduced. Reducing the size of the central cavity is substantially disadvantageous, since the volume of available air, the quantity of air contained within the central cavity, is reduced. This reduction of available air results in the increase of air pressures within the central cavity, causing a degradation in the quality of sound produced by the loudspeaker, and particularly degradation of the low frequency response of the loudspeaker.
Thus, there exists a need for a compression driver structure that enables the dimensions of a loudspeaker cover to be reduced without diminishing the quality of sound produced by the loudspeaker, and particularly without diminishing the low frequency response thereof.